OSU International Symposium on Molecular Spectroscopyhttp://hdl.handle.net/1811/5850
Sun, 02 Aug 2015 22:42:59 GMT2015-08-02T22:42:59ZA "WET DOG" TUNNELING MOTION AS THE CAUSE FOR THE DOUBLED ROTATIONAL SPECTRUM OF 1-IODONONAFLUOROBUTANEhttp://hdl.handle.net/1811/55615
A "WET DOG" TUNNELING MOTION AS THE CAUSE FOR THE DOUBLED ROTATIONAL SPECTRUM OF 1-IODONONAFLUOROBUTANE
Bailey, W. C.; Bohn, R. K.; Grubbs, G. S.; Kisiel, Z.; Cooke, S. A.
A chirped pulse Fourier transform microwave spectrometer has been used to record the rotational spectra of 1-iodononafluorobutane between 8 GHz and 12 GHz. The target compound was spectroscopically examined as it participated in a supersonic expansion of argon. The spectra recorded are dense owing in part to the small rotational constants, $B$ + $C$ $\approx$ 480 MHz, but also to hyperfine structure generated by the coupling of angular momenta of the iodine nucleus and the rotating molecular frame, e.g. $\mid \chi_{ab} \mid$ $\approx$ 1200 MHz. Notably all of the hyperfine components were observed as doublets. It is postulated that this doubling effect is the result of a low barrier, double minimum potential between two mirror image transoid structures. The tunneling motion between these structures resembles that of a "wet dog" shaking itself dry. Numerous transitions are shifted in frequency and it is proposed that the density of rotational energy levels from the two interacting states results in numerous perturbations to the energy levels involved. A preliminary spectral analysis of over 400 transitions will be presented, along with the results of supporting quantum mechanical calculations.
Author Institution: Chemistry-Physics Department (Retired), Kean University; Union, New Jersey, USA 07083; Departments of Chemistry and Physics, University of Connecticut,Storrs, Connecticut, 06269-3060, USA.; Department of Chemistry, Wesleyan University, Hall-Atwater Laboratories, 52 Lawn Ave, Middletown, Connecticut, 06459-0180, USA.; Institute of Physics, Polish Academy of Sciences, Al. Lotnikov 32146, 02-668 Warszawa, Poland.; School of Natural and Social Sciences, Purchase College SUNY, 735 Anderson Hill Road, Purchase, NY 10577, USA
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556152013-01-01T00:00:00ZBailey, W. C.Bohn, R. K.Grubbs, G. S.Kisiel, Z.Cooke, S. A.MW SYSTEMATIC STUDY OF ALKALOIDS: THE DISTORTED TROPANE OF SCOPOLINEhttp://hdl.handle.net/1811/55613
MW SYSTEMATIC STUDY OF ALKALOIDS: THE DISTORTED TROPANE OF SCOPOLINE
Ecija, Patricia; Cocinero, Emilio J.; Basterretxea, Francisco J.; Fernandez, Jose A.; Castano, Fernando; Lesarri, Alberto
Tropane alkaloids have diverse pharmacological uses and are well-known for their neurostimulant activity. Previous structure-activity-relationship established correlations between bioactivity and several aspects of ligand conformation and stereochemistry, including delicate intramolecular effects like nitrogen inversion$^{a}$. We have initiated a series of structural studies on tropane alkaloids$^{b}$, aimed to discerning their intrinsic stereochemical properties using rotational spectroscopy in supersonic jets$^{c}$. Here we extend these studies to the epoxytropanes, initially motivated to interrogate the influence of the epoxy group on nitrogen inversion and ring conformation. The rotational spectrum evidences a single structure in the gas phase, providing a first description of the (three ring) structurally-distorted tropane in scopoline. The determined rotational parameters of scopoline reveal the structural consequences of the intramolecular cyclation of scopine, which breaks the original epoxy group and creates a new ether bridge and a 7$\beta$-hydroxytropane configuration. The hydroxyl group further stabilizes the molecule by an $O-H \cdots N$ intramolecular hydrogen bond, which, in turn, forces the N-methyl group to the less stable axial form$^{b}$. The experimental work was supported by ab initio and DFT calculations.\\ $^{a}$ i) S.Singh, \emph{Chem. Rev.} 100, 925 (2000); ii) A. Krunic, D. Pan, W.J. Dunn III, S.V.S. Miariappan, \emph{Bioorg. &amp; Med. Chem.} 17, 811 (2009).\\ $^{b}$ E.J. Cocinero, A. Lesarri, P. Ecija, J.-U. Grabow, J.A. Fernandez, F. Casta\~{n}o, \emph{Phys. Chem. Chem. Phys.} 12, 6076 (2010).\\ $^{c}$ E.J. Cocinero, A. Lesarri, P. Ecija, J.-U. Grabow, J.A. Fernandez, F. Casta\~{n}o, \emph{Phys. Chem. Chem. Phys.} 12, 12486 (2010).
Author Institution: Departamento de Quimica Fisica, Facultad de Ciencia y Tecnologia, Universidad del Pais Vasco (UPV/EHU), Ap.644, E-48940, Bilbao, Spain; Departamento de Quimica Fisica y Quimica Inorganica, Facultad de Ciencias, Universidad de Valladolid, E-47011 Spain
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556132013-01-01T00:00:00ZEcija, PatriciaCocinero, Emilio J.Basterretxea, Francisco J.Fernandez, Jose A.Castano, FernandoLesarri, AlbertoSTRUCTURAL STUDIES OF PYRROLE-BENZENE COMPLEXES BY CHIRPED-PULSE ROTATIONAL SPECTROSCOPYhttp://hdl.handle.net/1811/55614
STRUCTURAL STUDIES OF PYRROLE-BENZENE COMPLEXES BY CHIRPED-PULSE ROTATIONAL SPECTROSCOPY
Lobsiger, Simon; Perez, Cristobal; Zaleski, Daniel P.; Seifert, Nathan A.; Pate, Brooks H.; Pfaffen, Chantal; Trachsel, Maria A.; Leutwyler, Samuel
Non-covalent intermolecular interactions are important in structural biology. The N-H $\cdots$ $\pi$ hydrogen bond between amino acid side chains is an important structural determinant and highly affects the secondary structure of proteins. The pyrrole-benzene complex can be viewed as a model system for studying these fundamental interactions. Previous IR and UV spectroscopic studies of the pyrrole-benzene complex by Dauster \textit{et al.} nderline{\textbf{10}}, 2827 (2008)} and Pfaffen \textit{et al.} nderline{\textbf{13}}, 14110 (2011)} support a T-shaped structure with an N-H $\cdots$ $\pi$ hydrogen bond to the benzene ring. In order to obtain accurate structural information we have investigated the broadband rotational spectrum of the supersonic-jet cooled complexes of pyrrole with benzene and benzene-\textit{d}$_{1}$ in the 2-18 GHz frequency range. In addition to the hetero dimer we have also observed the two cyclic mixed trimers (pyrrole)$_{2}$-benzene and pyrrole-(benzene)$_{2}$.
Author Institution: Department of Chemistry, University of Virginia, McCormick Rd., Charlottesville, VA 22904; Departement fur Chemie und Biochemie, Universitat Bern, Freiestrasse 3, 3012 Bern, Switzerland
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556142013-01-01T00:00:00ZLobsiger, SimonPerez, CristobalZaleski, Daniel P.Seifert, Nathan A.Pate, Brooks H.Pfaffen, ChantalTrachsel, Maria A.Leutwyler, SamuelGAS-PHASE STRUCTURES OF LINALOOL AND COUMARIN STUDIED BY MICROWAVE SPECTROSCOPYhttp://hdl.handle.net/1811/55612
GAS-PHASE STRUCTURES OF LINALOOL AND COUMARIN STUDIED BY MICROWAVE SPECTROSCOPY
Nguyen, H. V. L.; Stahl, W.; Grabow, J.-U.
The microwave spectra of two natural substances, linalool and coumarin, were recorded in the microwave range from 9 to 16 GHz and 8.5 to 10.5 GHz, respectively.Linalool is an acyclic monoterpene and the main component of lavender oil. It has a structure with many possible conformations. The geometry of the lowest energy conformer has been determined by a combination of microwave spectroscopy and quantum chemical calculations. Surprisingly, a globular rather than a prolate shape was found. This structure is probably stabilized by a $\pi$ interaction between two double bonds which are arranged in two stacked layers of atoms within the molecule. A-E splittings due to the internal rotation of one methyl group could be resolved and the barrier to internal rotation was determined to be 400.20(64) cm$^{-1}$. The standard deviation of the fit was close to experimental accuracy. For an identification of the observed conformer not only the rotational constants but also the internal rotation parameters of one of the methyl groups were needed. Coumarin is a widely used flavor in perfumery as sweet woodruff scent. The aromatic structure allows solely for one planar conformer, which was found under molecular beam conditions and compared to other molecules with similar structures. Here, the rotational spectrum could be described by a set of parameters including the rotational constants and the centrifugal distortion constants using a semi-rigid molecule Hamiltonian. Furthermore, the rotational transitions of all nine $^{13}$C isotopologues were measured in natural abundance. As a consequence, the microwave structure of coumarin could be almost completely determined.
Author Institution: Institut fur Physikalische Chemie, RWTH Aachen University, Landoltweg 2, 52074 Aachen, Germany; Institut fur Physikalische Chemie und Elektrochemie, Lehrgebiet A, Callinstrasse 3-3a, 30167 Hannover, Germany
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556122013-01-01T00:00:00ZNguyen, H. V. L.Stahl, W.Grabow, J.-U.INFRARED SPECTROSCOPY AND STRUCTURES OF MASS-SELECTED RHODIUM CARBONYL AND RHODIUM DINITROGEN CATIONShttp://hdl.handle.net/1811/55610
INFRARED SPECTROSCOPY AND STRUCTURES OF MASS-SELECTED RHODIUM CARBONYL AND RHODIUM DINITROGEN CATIONS
Abbott, Heather L.; Brathwaite, Antonio D.; Duncan, Michael A.
Rhodium carbonyl cations, Rh(CO)$_{n}^{+}$, and rhodium dinitrogen cations, Rh(N$_{2})_{n}^{+}$, are produced by laser vaporization in a pulsed-nozzle molecular beam source. Mass-selected infrared photodissociation spectroscopy of these ions and their argon tagged analogs are compared to density functional theory computations. Structures of the rhodium cations are determined based upon the number, frequency position and relative intensity of the infrared active bands between 2000 and 2400 cm$^{-1}$. Computed binding energies and fragmentation patterns suggest that four carbonyl ligands bind strongly to the central rhodium cation.
Author Institution: Department of Chemistry and Biochemistry, Kennesaw State University, Kennesaw, GA 30144; Department of Chemistry, University of Georgia, Athens, GA 30602-2256
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556102013-01-01T00:00:00ZAbbott, Heather L.Brathwaite, Antonio D.Duncan, Michael A.THE PROTOTYPE DIPEPTIDE GLY-GLY: A ROTATIONAL STUDYhttp://hdl.handle.net/1811/55611
THE PROTOTYPE DIPEPTIDE GLY-GLY: A ROTATIONAL STUDY
Varela, M.; Cabezas, C.; Mata, S.; Alonso, J. L.
The simplest dipeptide Gly-Gly has been examined for the first time in the gas phase by laser ablation molecular beam Fourier transform microwave (LA-MB-FTMW) spectroscopy. The nuclear quadrupole hyperfine structure of two $^{14}$N nuclei has been totally resolved allowing the conclusive identification of three conformers in the supersonic expansion. Intramolecular hydrogen bonding interactions have been analyzed on the bases of the structure of the observed conformers. Present results indicate that it is possible to face the study larger peptides using LA-MB-FTMW spectroscopy.
Author Institution: Grupo de Espectroscopia Molecular (GEM), Edificio Quifima, Laboratorios de Espectroscopia y Bioespectroscopia, Parque Cientifico, Universidad de Valladolid, 47011 Valladolid, Spain
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556112013-01-01T00:00:00ZVarela, M.Cabezas, C.Mata, S.Alonso, J. L.SLOW ELECTRON VELOCITY-MAP IMAGING OF La$_2$(C$_6$H$_6$) AND La(C$_6$H$_6$)$_2$http://hdl.handle.net/1811/55609
SLOW ELECTRON VELOCITY-MAP IMAGING OF La$_2$(C$_6$H$_6$) AND La(C$_6$H$_6$)$_2$
Silva, Ruchira; Yang, Dong-Sheng
Slow electron velocity-map imaging (SEVI) was used to study the structures and electronic states of La$_2$(C$_6$H$_6$) and La(C$_6$H$_6$)$_2$ complexes formed in a metal cluster beam source. Electron spectra obtained from SEVI have the energy resolution of $\Delta$E/eKE $\approx$ 2$\%$ at eKE=400cm$^{-1}$. The SEVI technique offers much higher data collection efficiency than pulsed-field ionization zero electron kinetic energy spectroscopy. From the SEVI spectra, adiabatic ionization energies were measured to be 32141(5) cm$^{-1}$ for La$_2$(C$_6$H$_6$) and 39033(5) cm$^{-1}$ for La(C$_6$H$_6$)$_2$. The most active vibrational transition for both complexes was identified to be a metal-ligand stretching mode with a frequency of 180 cm$^{-1}$ in the ion state. In addition, a benzene ring out-of-plane deformation mode was measured to be 303 cm$^{-1}$ for [La$_2$(C$_6$H$_6$)]$^+$ and 408 cm$^{-1}$ for [La(C$_6$H$_6$)$_2$]$^+$. By combining the spectra with theoretical calculations, we identified the $^2$A$_g$$\leftarrow$$^1$A$_g$ transition of La$_2$(C$_6$H$_6$) (C$_{2h}$) and $^3$A$\leftarrow$$^2$A of La(C$_6$H$_6$)$_2$ (C$_1$). By measuring the anisotropy parameter ($\beta$) from photoelectron angular distribution, we found that the outgoing electron was from a largely La 6s-based molecular orbital in both complexes.
Author Institution: Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556092013-01-01T00:00:00ZSilva, RuchiraYang, Dong-ShengUNDERSTANDING COMPLEX SPECTRAL SIGNATURES OF EMBEDDED EXCESS PROTONS IN MOLECULAR SCAFFOLDS WITH THIRD ORDER CORRECTIONS TO THE HARMONIC POTENTIAL SURFACEhttp://hdl.handle.net/1811/55608
UNDERSTANDING COMPLEX SPECTRAL SIGNATURES OF EMBEDDED EXCESS PROTONS IN MOLECULAR SCAFFOLDS WITH THIRD ORDER CORRECTIONS TO THE HARMONIC POTENTIAL SURFACE
Deblase, Andrew F.; Johnson, Mark A.; Lectka, Thomas; Wang, Xun; Jordan, Kenneth D.; McCoy, Anne B.
Overtones and combination bands observed in vibrational predissociation spectra of cold ions can often be anticipated by expanding the potential energy surface to third order. This is achieved by relating the third derivatives to the matrix elements that couple the allowed and forbidden states in the harmonic basis. Such a strategy has been successful in predicting Fermi resonances in formic acid clusters and some charged H-bonded complexes. Furthermore, third order couplings have been used to develop a vibrational adiabatic model in which excitation of a bright state is distributed over a Franck-Condon envelop of a lower energy mode, such as a water rocking against triatomic domains of molecular anions. Previous applications include the analysis of long vibrational progressions of soft modes in the OH stretching region of the actetate-water binary complex. Here we explore to extent to which this order of correction captures the irregular patterns associated with intramolecular proton bonds.
Author Institution: Yale University, P.O. Box 208107, New Haven, CT 06520, USA; Johns Hopkins University, 3400 North Charles Street, Baltimore, Maryland 21218, USA; University of Pittsburgh, 219 Parkman Avenue, Pittsburgh, PA 15260, USA; The Ohio State University, Columbus, Ohio 43210, USA
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556082013-01-01T00:00:00ZDeblase, Andrew F.Johnson, Mark A.Lectka, ThomasWang, XunJordan, Kenneth D.McCoy, Anne B.HIGH-RESOLUTION PHOTOELECTRON SPECTROSCOPY OF 2-BUTYNEhttp://hdl.handle.net/1811/55607
HIGH-RESOLUTION PHOTOELECTRON SPECTROSCOPY OF 2-BUTYNE
Jacovella, Ugo; Gans, Berenger; Merkt, Frederic
Using a coherent narrow-band vacuum-ultraviolet (VUV) laser source (bandwitdh of 0.008~cm$^{-1}$)$ \textbf{71}, 4023 (2000).}$ coupled to a photoionization and pulse-field-ionization zero-kinetic-energy photoelectron (PFI-ZEKE) spectrometer, the threshold photoionization of polyatomic molecules can be studied at high resolution. We present a new measurement of the PFI-ZEKE photoelectron spectrum of the origin band of the X$^+$~$^2$E$_{2(d)}$ $\leftarrow$~X~$^1\mathrm{A}_{1(s)}$ ionizing transition of 2-butyne at a resolution of 0.15~cm$^{-1}$. Despite this high resolution, the spectral congestion originating from the combined effects of the internal rotation, the spin-orbit coupling and the Jahn-Teller effect prevented the full resolution of the rotational structure of the photoelectron spectrum. Combined with the known structure of the X $^1$A$_{1(s)}$ ground state of 2-butyne, including the free internal rotation$ \textbf{6}, 445 (1963).}$$ \textbf{37}, 1433 (1962).}$$ \textbf{8}, 81 (1964).}$, the spectrum was used to derive information on the X$^+$~$^2$E$_{2(d)}$ ground state of the 2-butyne radical cation. The rotational branch structure of the spectrum points at a complex energy-level structure of the cation and at the importance of a shape resonance enhancing g photoelectron partial waves$ \textbf{136}, 154303 (2012).}$.
Author Institution: ETH Zurich, Laboratorium fur Physikalische Chemie, Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556072013-01-01T00:00:00ZJacovella, UgoGans, BerengerMerkt, FredericC-C BOND ACTIVATION AND COUPLING OF PROPENE INDUCED BY LA ATOMhttp://hdl.handle.net/1811/55606
C-C BOND ACTIVATION AND COUPLING OF PROPENE INDUCED BY LA ATOM
Hewage, Dilrukshi; Tao, Hong; Silva, Ruchira; Kumari, Sudesh; Yang, Dong-Sheng
A series of La(C$_n$H$_m$) complexes with n $\leq$ 6 and m $\leq$ 12 were produced by the reactions between propene and La in a supersonic molecular beam source. Their formation and structures were investigated using mass-analyzed threshold ionization (MATI) spectroscopy in combination with theoretical calculations. Previously, we identified the formation of La(C$_3$H$_4$) and H-La(C$_3$H$_5$) through dehydrogenation and metal insertion mechanisms. In this work, we will discuss the formation of La(CH$_2$) and La(C$_4$H$_6$) by La induced C-C bond activation and coupling. La(CH$_2$) is formed by the C-C bond breakage and 1,2-hydride shift of propene and is a Schrock-type carbene complex. This complex is then coupled with the C=C bond of a second propene molecule to form La(C$_4$H$_6$) by removing two hydrogen atoms. The resultant La(C$_4$H$_6$) complex was idetified in two low-energy isomeric forms: one was a metallacycle (isomer A) and the other was lanthanum trimethylenemethane (isomer B). Both La(C$_4$H$_6$) isomers are in a doublet ground state, with isomer A in C$_s$ point group and isomer B in C$_3$$_v$. Adiabatic ionization energies and several vibrational frequencies of the two complexes were obtained from the sharp MATI spectra.
Author Institution: Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055; Department of Chemistry, Southwest Forestry University, Kunming 650224, PR China; Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556062013-01-01T00:00:00ZHewage, DilrukshiTao, HongSilva, RuchiraKumari, SudeshYang, Dong-ShengTORSION-ROTATION-VIBRATION EFFECTS IN THE $\nu_{20}$, 2$\nu_{21}$, 2$\nu_{13}$ AND $\nu_{21} + \nu_{13}$ STATES OF CH$_3$CH$_2$CNhttp://hdl.handle.net/1811/55605
TORSION-ROTATION-VIBRATION EFFECTS IN THE $\nu_{20}$, 2$\nu_{21}$, 2$\nu_{13}$ AND $\nu_{21} + \nu_{13}$ STATES OF CH$_3$CH$_2$CN
Daly, Adam M.; Pearson, John C.; Yu, Shanshan; Drouin, Brian J.; Bermudez, C.; Alonso, J. L.
Ethyl cyanide, CH$_3$CH$_2$CN, is a highly abundant molecule in hot cores associated with massive star formation where temperatures often approach 200K. Astrophysicists would like to use the many thousands of observed lines to evaluate thermal equilibrium, temperature distributions, heating sources, and radiative pumping effects. In spite of a recent partial success in characterizing the $\nu_{20}$ and $\nu_{12}$ vibrational states~(2013) in press.}, many aspects of the spectroscopy of the $\nu_{20}$ state are not adequately characterized. Torsional splittings in the b-type spectrum of $\nu_{20}$ are typically a few MHz and many a-type transitions also show resolved torsional splittings, both are incompatible with the expected 1200 cm$^{-1}$ barrier to internal rotation in a $v_t=0$ state. Additionally all $K$ values above 2 show some obvious perturbations. The three states that lie just above $\nu_{20}$ are 2$\nu_{21}$, 2$\nu_{13}$ and $\nu_{21} + \nu_{13}$. It has been determined that $\nu_{20}$ interacts weakly with both 2$\nu_{21}$ and 2$\nu_{13}$ and that 2$\nu_{21}$ interacts weakly with 2$\nu_{13}$, in spite of their common symmetry and very close proximity. However, all the interactions of $\nu_{21} + \nu_{13}$ appear to be very strong, making assignments of the combination band particularly problematic. The numerous interactions result in wide spread anomalous torsional splittings. These splittings provide valuable insight into the nature of the interactions, however without a reasonable model, assignment of A or E to a torsional component is far from obvious. There remains no reasonable quantum mechanical description of how to proceed with a torsion-rotation-vibration analysis involving large and small amplitude motions. Regardless, everything that can be assigned in the laboratory spectrum can be securely identified in the astronomical spectrum of several sources, suggesting that a solution to this problem is needed. We present what is known and unknown in this quartet of CH$_3$CH$_2$CN states.
Author Institution: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109; Grupo de Espectroscopia Molecular (GEM), Edificio Quifima, Laboratorios de Espectroscopia y Bioespectroscopia, Parque Cientfico, Universidad de Valladolid, 47011 Valladolid, Spain
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556052013-01-01T00:00:00ZDaly, Adam M.Pearson, John C.Yu, ShanshanDrouin, Brian J.Bermudez, C.Alonso, J. L.MASS ANALYZED THRESHOLD IONIZATION OF LUTETIUM DIMERhttp://hdl.handle.net/1811/55604
MASS ANALYZED THRESHOLD IONIZATION OF LUTETIUM DIMER
Wu, Lu; Roudjane, Mourad; Liu, Yang; Yang, Dong-Sheng
Lu$_2$ is produced in a pulsed laser-vaporization metal-cluster source and studied by mass-analyzed threshold ionization (MATI) spectroscopy. The MATI spectrum displays several long progressions from the transitions between various vibrational levels of the neutral and ion electronic states. From the spectrum, the upper limit of the ionization energy of the dimer is determined to be 43996 cm$^{-1}$, and the vibrational frequencies are measured to be 121 cm$^{-1}$ in the neutral state and 90 cm$^{-1}$ in the ion state. By combining with ab initio calculations at CASPT2 level, the ground state of Lu$_2$ is identified as $^3\Sigma_g^-$. The $^3\Sigma_g^-$ state has an electron configuration of 6s$\sigma_g^2$5d$\pi_u^1$5d$\pi_u^1$6s$\sigma_u^2$, which is formed by the interactions of two Lu atoms in the $^2$D(5d6s$^2$) ground state. Ionization of the neutral state removes a 5d$\pi$$_u$ bonding electron and yields a ion state with a considerably longer bond distance. Lu$_2$ has a very different bonding feature from La$_2$, for which a $^1\Sigma_g^+$ ground state was previously identified with an electron configuration of 5d$\pi_u^4$6s$\sigma_g^2$ formed by the interactions of two La atoms in the $^4$F(5d$^2$6s) excited state. \textbf{135}, 034309 (2011).}
Author Institution: Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556042013-01-01T00:00:00ZWu, LuRoudjane, MouradLiu, YangYang, Dong-ShengUBIQUITOUS INTERSTELLAR MOLECULES WITH RADICALLY DIFFERENT CATION STRUCTURES: INFRARED SPECTROSCOPY OF FORMALDEHYDE AND METHANOL CATIONShttp://hdl.handle.net/1811/55602
UBIQUITOUS INTERSTELLAR MOLECULES WITH RADICALLY DIFFERENT CATION STRUCTURES: INFRARED SPECTROSCOPY OF FORMALDEHYDE AND METHANOL CATIONS
Mosley, Jonathan D.; Duncan, Michael A.
Formaldehyde and methanol are detected in interstellar and circumstellar sources by rotational transitions resulting from their well-known structures. For the radical cations with nominal formulas $[C,H_2,O]^+$ and $[C,H_4,O]^+$, no such measurements have been made in interstellar sources or in the laboratory to our knowledge. We measured the infrared spectrum of both radical cations in the gas phase using infrared photodissociation spectroscopy and found structures that differ drastically from the neutral closed shell species. For the case of $[C,H_2,O]^+$, formaldehyde cation $CH_2O^+$ and hydroxymethylene cation $CHOH^+$ are predicted to be minima with only ~5 kcal/mol difference in stability. We see evidence for two isomers in the infrared spectrum and investigate the effects of the argon tag on these small (four atoms) radical cations. For the mass 32 cation $[C,H_4,O]^+$, theory predicts the methyleneoxonium cation $CH_2OH_2^+$ to be about 15 kcal/mol more stable than the methanol cation $CH_3OH^+$. We present definitive assignments of vibrational features to these two isomers of the mass 32 cation. We discuss the kinetic trapping occurring in the ion source that produce the thermodynamically unfavorable $CH_3OH^+$ simultaneously with the lowest energy structure, $CH_2OH_2^+$. The application of our findings to astrochemistry is discussed.
Author Institution: University of Georgia, Athens, GA 30683
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556022013-01-01T00:00:00ZMosley, Jonathan D.Duncan, Michael A.THE CORONENE VIBRONIC STATES ABOVE THE FIRST IONIZATION POTENTIAL INVESTIGATED THROUGH TPEPICO EXPERIMENTShttp://hdl.handle.net/1811/55603
THE CORONENE VIBRONIC STATES ABOVE THE FIRST IONIZATION POTENTIAL INVESTIGATED THROUGH TPEPICO EXPERIMENTS
Brechignac, Ph.; Falvo, C.; Parneix, P.; Pino, T.; Pirali, O.; Garcia, G.; Nahon, L.; Joblin, C.; Kokkin, D.; Bonammy, A.; Mulas, G.
Threshold Photoelectron spectra (TPES), as well as Total Ion Yeld (TIY) spectra of jet-cooled Coronene ($C_{12}H_{24}$) have been obtained using the electron/ion coincidence imaging spectrometer DELICIOUS II available at the DESIRS beamline of the French Synchrotron facility SOLEIL. The obtained data can be interpreted in the light of new theoretical DFT and TDDFT based calculations. They will be discussed in comparison to available photoelectron (PES) and optical absorption data. New autoionizing neutral states have also been observed and their relaxation to final cationic states characterized.
Author Institution: Institut des Sciences Moleculaires d'Orsay, CNRS UMR8214, Univ Paris-Sud, Bat 210, F91405 Orsay Cedex, France; Synchrotron SOLEIL, L' Orme des Merisiers, St Aubin, B.P. 48, 91192 Gif sur Yvette, France; IRAP, Universite de Toulouse [UPS], CNRS, Toulouse, France; INAF-Osservatorio Astronomico di Cagliari-Astrochemistry Group, Strada 54, Localita Poggio dei Pini, I-09012 Capoterra (CA), Italy
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556032013-01-01T00:00:00ZBrechignac, Ph.Falvo, C.Parneix, P.Pino, T.Pirali, O.Garcia, G.Nahon, L.Joblin, C.Kokkin, D.Bonammy, A.Mulas, G.INFRARED SPECTROSCOPY OF THE MASS 43 CATION: ACETYL CATION AND PROTONATED KETENEhttp://hdl.handle.net/1811/55601
INFRARED SPECTROSCOPY OF THE MASS 43 CATION: ACETYL CATION AND PROTONATED KETENE
Mosley, Jonathan D.; Duncan, Michael A.
The mass 43 cation $[C_2,H_3,O]^+$ is prominent in mass spectra of organic molecules. Theory predicts no less than nine structural isomers, and the acetyl cation $CH_3CO^+$ is the global minimum. The infrared spectrum of the mass 43 cation from methyl acetate shows vibrations only from the acetyl cation. The effects of the methyl free internal rotor are discussed. The mass 43 cation from acetone shows evidence for both the acetyl cation and the less thermodynamically stable (~50 kcal/mol) protonated ketene isomer $CH_2COH^+$. The effects of varying the kinetic trapping conditions in our ion source on isomeric ratios of the mass 43 cation are discussed.
Author Institution: University of Georgia, Athens, GA 30683
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556012013-01-01T00:00:00ZMosley, Jonathan D.Duncan, Michael A.HIGH PRECISION SPECTROSCOPY OF CH$_5^+$ USING NICE-OHVMShttp://hdl.handle.net/1811/55600
HIGH PRECISION SPECTROSCOPY OF CH$_5^+$ USING NICE-OHVMS
Hodges, James N.; Perry, Adam J.; McCall, Benjamin J.
The elusive methonium ion, CH$_5^+$, is of great interest due to its highly fluxional nature. The only published high-resolution infrared spectrum remains completely unassigned to this date. (1999) \textbf{284}, 135--137. } The primary challenge in understanding the CH$_5^+$ spectrum is that traditional spectroscopic approaches rely on a molecule having only small (or even large) amplitude motions about a well-defined reference geometry, and this is not the case with CH$_5^+$. \vspace{1em} We are in the process of re-scanning Oka's spectrum, in the original Black Widow discharge cell, using the new technique of Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy (NICE-OHVMS). \emph{Opt. Express} (2011), \textbf{19}, 24822--24827.} \emph{Chem. Phys. Lett.} (2012), \textbf{551}, 1--6.} The high precision afforded by optical saturation in conjunction with a frequency comb allows transition line centers to be determined with sub-MHz accuracy and precision -- a substantial improvement over the 90 MHz precision of Oka's work. \vspace{1em} With a high-precision linelist in hand, we plan to search for four line combination differences to directly determine the spacings between rotational energy levels. Such a search is currently infeasible due to the large number of false positives resulting from the relatively low precision and high spectral density of Oka's spectrum. The resulting combination differences, in conjunction with state-of-the-art theoretical calculations from Tucker Carrington,, (2008), \textbf{129}, 234102.} may provide the first insight into the rotational structure of this unique molecular system.
Author Institution: Department of Chemistry, University of Illinois, Urbana, IL 61801; Departments of Chemistry, Astronomy, and Physics, University of Illinois, Urbana, IL 61801
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/556002013-01-01T00:00:00ZHodges, James N.Perry, Adam J.McCall, Benjamin J.SUB-DOPPLER SPECTROSCOPY OF H$_3^+$http://hdl.handle.net/1811/55599
SUB-DOPPLER SPECTROSCOPY OF H$_3^+$
Hodges, James N.; Perry, Adam J.; Siller, Brian M.; McCall, Benjamin J.
Spectroscopy of H$_3^+$ is of fundamental interest for advancing \textit{ab initio} efforts to calculate spectra with high precision and accuracy. H$_3^+$ is the simplest polyatomic ion, which is why it is an excellent benchmark for theory. In order to perform calculations with spectroscopic accuracy, relativistic and non-adiabatic corrections to the Born-Oppenhiemer approximation must be included; calculations with these considerations agree to within hundredths of a wavenumber. (1999), \textbf{110}, 5056--5064.} Increasing the precision of the calculations further will require a treatment of quantum electrodynamic effects, as has already been implemented for the diatomic case, \emph{J. Chem. Theor. Comp.} (2011), \textbf{7}, 3105--3115.} and testing these calculations will require higher-precision experimental data to guide \textit{ab initio} calculations. \vspace{1em} Noise Immune Cavity Enhanced Optical Heterodyne Velocity Modulation Spectroscopy, or NICE-OHVMS \emph{Opt. Express} (2011), \textbf{19}, 24822--7.} \emph{Chem. Phys. Lett.} (2012), \textbf{551}, 1--6.}, is a highly sensitive, highly precise technique that we have employed to observe transitions in the $\nu_2$ fundamental band of H$_3^+$. It combines the advantages of cavity enhancement and heterodyne detection with the ion-neutral discrimination afforded by velocity modulation. Combining a cavity with a high power mid-infrared light source, we can saturate rovibrational transitions. The resulting Lamb dips may be fit in order to determine line centers to a much higher precision than is possible for ordinary Doppler broadened profiles. Additionally, a frequency comb is used to surpass the limited accuracy and precision of a wavemeter. Here we present the results from comb calibrated H$_3^+$ transitions observed via NICE-OHVMS. Precision and accuracy of $\sim$ 1 MHz were achieved representing the most accurate and precise H$_3^+$ line list that has been obtained to date.
Author Institution: Department of Chemistry, University of Illinois, Urbana, IL 61801; Departments of Chemistry, Astronomy, and Physics, University of Illinois, Urbana, IL 61801
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555992013-01-01T00:00:00ZHodges, James N.Perry, Adam J.Siller, Brian M.McCall, Benjamin J.PRECISION LASER SPECTROSCOPY OF H$_3^+$http://hdl.handle.net/1811/55598
PRECISION LASER SPECTROSCOPY OF H$_3^+$
Chen, Hsuan-Chen; Peng, Jin-Long; Amano, T.; Shy, Jow-Tsong
The high-resolution sub-Doppler Lamb dips of the $\nu_2$ fundamental band transitions of H$_3^+$ have been observed using an extended negative glow discharge tube as an ion source and a periodically poled lithium niobate optical parametric oscillator as a radiation source.,{~\bf 109},~263002~(2012)} The absolute frequencies of five transitions were measured to an accuracy of 250 kHz using a fiber optical frequency comb. In addition, we measured the homogeneous linewidths of these lines. Physical significance of these results will be discussed in terms of collisional processes.
Author Institution: Institute of Photonics Technologies, National Tsing Hua University, Hsinchu 30013, Taiwan; Center for Measurement Standards, Industrial Technology Research Institute, Hsinchu 30011, Taiwan; Department of Chemistry and Department of Physics and Astronomy; University of Waterloo, Waterloo, ON N2L 3G1, Canada; Institute of Photonics Technologies, National Tsing Hua University and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555982013-01-01T00:00:00ZChen, Hsuan-ChenPeng, Jin-LongAmano, T.Shy, Jow-TsongINFRARED SPECTROSCOPY OF JET COOLED ND$_2$H$_2^{+}$ MOLECULAR IONS: THE SYMMETRIC AND ANTISYMMETRIC NH STRETCH MODEShttp://hdl.handle.net/1811/55597
INFRARED SPECTROSCOPY OF JET COOLED ND$_2$H$_2^{+}$ MOLECULAR IONS: THE SYMMETRIC AND ANTISYMMETRIC NH STRETCH MODES
Chang, Chih-Hsuan; Nesbitt, David J.
Rovibrational progressions in the symmetric ($v$$_6$) and antisymmetric ($v$$_1$) NH stretching modes of the ND$_2$H$_2^{+}$ molecular ion are observed for the first time, exploiting the i) high ion density and ii) high resolution capabilities of our slit jet discharge infrared spectrometer. These isotopomeric ions are generated by striking a modulated (50 KHz) electrical discharge in a mixture of ND$_3$/H$_2$O/H$_2$ gases, achieving a modulated ion density suitable for time-gated, lock-in detection in the throat of a long path slit-jet expansion. Assignment of both $b$-type and $c$-type bands enables high accuracy determination of the rotational constants ($A$$^{\prime\prime}$=4.85598(19), $B$$^{\prime\prime}$=3.96811(11), and $C$$^{\prime\prime}$=3.44661(40) cm$^{-1}$), with band origins for $v$$_1$ and $v$$_6$ modes determined to be 3297.54367(34) and 3337.90456(33) cm$^{-1}$, respectively. The results prove to be in good agreement with anharmonically corrected predictions from ${ab}$ initio quartic force fields of Martin and Lee.
Author Institution: JILA, National Institute of Standards and Technology; University of Colorado, and Department of Chemistry and Biochemistry; University of Colorado at Boulder, Colorado 80309
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555972013-01-01T00:00:00ZChang, Chih-HsuanNesbitt, David J.SUB-DOPPLER SPECTROSCOPY OF ND$_3$H$^{+}$ ION IN THE NH STRETCHING MODEhttp://hdl.handle.net/1811/55596
SUB-DOPPLER SPECTROSCOPY OF ND$_3$H$^{+}$ ION IN THE NH STRETCHING MODE
Chang, Chih-Hsuan; Buckingham, Grant T.; Nesbitt, David J.
Despite early successes with velocity modulation spectroscopy$^{,}$of ammonium (NH$_4^{+}$ ) and perdeuteroammonium (ND$_4^{+}$) cation, corresponding studies of any of the mixed H/D isotopomers (NH$_m$D$_{4-m}^{+}$) have proven elusive. In this talk, we present first high resolution results on the lone NH stretch fundamental mode for the jet cooled ND$_3$H$^{+}$ ion, based on tunable IR difference frequency absorption spectroscopy in a slit jet, sub-Doppler resolution infrared spectrometer. Supersonically cooled ND$_3$H$^{+}$ ions are generated by modulated (50 KHz) discharges (650V, 500 mA) in ND$_3$ doped H$_2$/Ne slit jet expansions, monitored by time-gated, lock-in detection methods and with absorption sensitivities near the quantum shot noise limit. Jet cooled (30 K) $P$, $Q$, and $R$ branch rovibrational progressions in the $a$-type NH stretch band are observed and unambiguously assigned by four line ground state combination differences, with additional confirmation by nuclear spin statistical weights for the 3 identical D atoms (I = 1). Least squares fits to this parallel band yield precision rotational constants and an NH stretch vibrational band origin at 3316.8347(19) cm$^{-1}$. These high resolution spectroscopic results prove to be in generally excellent agreement with high level ${ab}$ initio theoretical predictions by Martin and Lee.
Author Institution: JILA, National Institute of Standards and Technology; University of Colorado, and Department of Chemistry and Biochemistry; University of Colorado at Boulder, Colorado 80309
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555962013-01-01T00:00:00ZChang, Chih-HsuanBuckingham, Grant T.Nesbitt, David J.FOURIER TRANSFORM FAR-INFRARED SPECTROSCOPY OF HN$_2^+$ ON THE AILES BEAMLINE OF SYNCHROTRON SOLEILhttp://hdl.handle.net/1811/55595
FOURIER TRANSFORM FAR-INFRARED SPECTROSCOPY OF HN$_2^+$ ON THE AILES BEAMLINE OF SYNCHROTRON SOLEIL
Pirali, O.; Grue, S.; Vervloet, M.
We report the pure rotation spectrum of HN$_2^+$ measured by Fourier Transform (FT) absorption spectroscopy in the 20-40 cm$^{-1}$ spectral range. The cations are produced in a liquid nitrogen cooled hollow cathode discharge cell developed on the AILES beamline of synchrotron SOLEIL. The set-up was optimized by recording rotation-vibration spectra of H$_3^+$($\nu_2$ band centered at 2521 cm$^{-1}$), HN$_2^+$ ($\nu_1$ band centered at 3234 cm$^{-1}$) and HCO$^+$($\nu_1$ band centered at 3089 cm$^{-1}$). Many rotation-vibration lines have been assigned for each ion and 5 pure rotational transitions have been detected for HN$_2^+$. These results demonstrate the feasibility to record far-infrared (far-IR) spectra of cationic species using FT broad band spectroscopy associated to the bright synchrotron radiation continuum as an alternative to laser-based frequency tunable techniques. In the presentation, we will describe the experimental set-up, the results obtained and the perspectives of this preliminary work which will rely on the exploitation of intense Coherent Synchrotron Radiation (CSR).
Author Institution: Ligne AILES, Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, 91192 Gif sur Yvette Cedex - France
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555952013-01-01T00:00:00ZPirali, O.Grue, S.Vervloet, M.MILLIMETER-WAVE SPECTROSCOPY OF AMINOMALONONITRILEhttp://hdl.handle.net/1811/55594
MILLIMETER-WAVE SPECTROSCOPY OF AMINOMALONONITRILE
Motiyenko, Roman A.; Margules, Laurent; Guillemin, Jean-Claude
In low-temperature conditions of the interstellar medium pure HCN and mixtures of HCN with H$_2$O and NH$_3$ subjected to high-energy sources can be converted into different HCN polymers, 2004, 170, 203}. In this context the HCN trimer -- aminomalononitrile (AMN, H$_2$NCH(CN)$_2$) is an interesting candidate for astrophysical detection. We measured the rotational spectrum of AMN using the Lille BWO-based fast scan spectrometer (120 -- 180 GHz) and the spectrometer based on solid state sources (225 -- 250 GHz). The spectroscopic work was supported by high level \textit{ab initio} calculations. The spectra observed were assigned only to the asymmetric conformer. The first analysis revealed the regular doublet splittings of rotational lines indicating the possibility of large-amplitude motion (LAM) of amino group. Further examination of the spectra revealed the existence of additional splittings most probably due to the second LAM of amino group. Since the equilibrium structure of AMN has no symmetry, in the group theoretical formalism these two LAMs can be described using G$_4$ permutation-inversion group. Despite the complexity of the LAMs all the assigned rotational transitions were fitted within experimental accuracy using Pickett's SPFIT program. As a result, a reliable dataset for astrophysical observations was provided.
Author Institution: Laboratoire PhLAM, UMR 8523 CNRS - Universite Lille 1, 59655 Villeneuve d'Ascq Cedex, France; Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS - ENSCR, 35708 Rennes Cedex 7, France.; This work is supported by the French program "Physique et Chimie du Milieu Interstellaire (PCMI, INSU-CNRS)" and the Centre National d'Etudes Spatiales (CNES).
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555942013-01-01T00:00:00ZMotiyenko, Roman A.Margules, LaurentGuillemin, Jean-ClaudeCOMBINATION BANDS BETWEEN 2900 AND 3600 CM$^{-1}$ OF CYCLIC O$_4$ CATION TRAPPED IN SOLID NEONhttp://hdl.handle.net/1811/55593
COMBINATION BANDS BETWEEN 2900 AND 3600 CM$^{-1}$ OF CYCLIC O$_4$ CATION TRAPPED IN SOLID NEON
Jacox, Marilyn E.; Thompson, Warren E.
The infrared spectrum of cyc-O$_4$$^+$ trapped in solid neon includes a group of combination bands built on {(\nu$_1$ + \nu$_5$)} of ground-state cyc-O$_4$$^+$. Each peak lies close to a counterpart previously reported in a study of the infrared laser photodissociation spectroscopy of a mass-selected molecular beam. This agreement is consistent with the vibrational assignment of three low-frequency modes of cyc-O$_4$$^+$ that was proposed in the earlier study. The spectra obtained for the isotopologues formed by the substitution of one or two $^{18}$O$_2$ moieties suggest the occurrence of interaction with a nearby excited electronic state.
Author Institution: Sensor Science Division, National Institute of Standards and Technology, Gaithersburg, MD 20899-8441
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555932013-01-01T00:00:00ZJacox, Marilyn E.Thompson, Warren E.PRECISION MEASUREMENT OF THE IONIZATION ENERGY OF THE $GK ^1\Sigma_g^+ (v=1,N=1)$ STATE OF MOLECULAR HYDROGEN.http://hdl.handle.net/1811/55591
PRECISION MEASUREMENT OF THE IONIZATION ENERGY OF THE $GK ^1\Sigma_g^+ (v=1,N=1)$ STATE OF MOLECULAR HYDROGEN.
Beyer, M.; Sprecher, D.; Merkt, F.
The ionization energy of the $GK~^1\Sigma_g^+~(v=1,N=1)$ state of ortho H$_2$ has been determined at a precision of 1.2~MHz by near-infrared laser spectroscopy. The measurement was performed by first exciting molecular hydrogen from the $X~^1\Sigma_g^+~(v=0,N=1)$ state to the $GK~^1\Sigma_g^+~(v=1,N=1)$ state in a resonant two-photon process via the $B~^1\Sigma_u^+~(v=3,N=2)$ state and then measuring the frequency of the transition between the $GK~^1\Sigma_g^+~(v=1,N=1)$ state and the 56p~$(S=0,N=1)$ Rydberg state belonging to the series converging on the $X^+~^2\Sigma_g^+~(v^+=0,N^+=1)$ ground state of ortho H$_2^+$. The ionization energy of the $GK~^1\Sigma_g^+~(v=1,N=1)$ state was obtained by adding this frequency to the binding energy of the 56p~$(S=0,N=1)$ Rydberg state which has been determined previously by millimeter-wave spectroscopy and multichannel quantum-defect theory \textbf{121} (23), 11810 (2004).} \textbf{150}, 51 (2011).}. For the measurement we used a homebuilt pulsed NIR laser with Fourier-transform-limited linewidth and adjustable pulse duration. To reach the desired accuracy, systematic errors originating from ac and dc Stark shifts, from pressure shifts, and from the frequency shifts and chirps accompanying the generation of the NIR laser pulses were quantified. The ionization energy of the $GK~^1\Sigma_g^+~(v=1,N=1)$ state will be compared with earlier results \textbf{93} (4), 2289 (1990).} \textbf{108} (7-9), 827 (2010).}. New attempts of measuring the binding energy of the $EF~^1\Sigma_g^+$ state will also be mentioned.
Author Institution: ETH Zurich, Laboratorium fur Physikalische Chemie, Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555912013-01-01T00:00:00ZBeyer, M.Sprecher, D.Merkt, F.QED TESTS AND SEARCH FOR NEW PHYSICS IN MOLECULAR HYDROGENhttp://hdl.handle.net/1811/55592
QED TESTS AND SEARCH FOR NEW PHYSICS IN MOLECULAR HYDROGEN
Salumbides, E. J.; Niu, M. L.; Dickenson, G. D.; Eikema, K. S. E.; Komasa, J.; Pachucki, K.; Ubachs, W.
The hydrogen molecule has been the benchmark system for quantum chemistry, and may provide a test ground for new physics. We present our high-resolution spectroscopic studies on the $X\,^1\Sigma^+_g$ electronic ground state rotational series, 043005 (2011).} and fundamenal vibrational tones in molecular hydrogen. In combination with recent accurate \emph{ab initio} calculations, we demonstrate systematic tests of quantum electrodynamical (QED) effects in molecules. Moreover, the precise comparison between theory and experiment can provide stringent constraints on possible new interactions that extend beyond the Standard Model.
Author Institution: Department of Physics and Astronomy, and LaserLaB, VU University, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands; Faculty of Chemistry, A. Mickiewicz University, Grunwaldzka 6, 60-780 Poznan, Poland; Faculty of Physics, University of Warsaw, Hoza 69, 00-681 Warsaw, Poland; Department of Physics and Astronomy, and LaserLaB, VU University, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555922013-01-01T00:00:00ZSalumbides, E. J.Niu, M. L.Dickenson, G. D.Eikema, K. S. E.Komasa, J.Pachucki, K.Ubachs, W.QED EFFECTS IN H$_2$http://hdl.handle.net/1811/55590
QED EFFECTS IN H$_2$
Pachucki, Krzysztof; Komasa, Jacek
The electron self-interaction and the vacuum polarization, the two effects predicted by Quantum Electrodynamics (QED), have been accurately calculated for H$_2$ and its isotopomers, 3105 (2011)}. The resulting theoretical predictions will be compared with state of the art measurements of dissociation energies, vibrational and rotational transitions. New developments for the calculation of higher order QED effects will be presented.
Author Institution: Faculty of Physics, University of Warsaw; Ho\.za 69, 00-681 Warsaw, Poland; Faculty of Chemistry, A. Mickiewicz University; Grunwaldzka 6, 60-780 Poznan, Poland
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555902013-01-01T00:00:00ZPachucki, KrzysztofKomasa, JacekNON-ADIABATIC ENERGIES OF THE HYDROGEN MOLECULEhttp://hdl.handle.net/1811/55589
NON-ADIABATIC ENERGIES OF THE HYDROGEN MOLECULE
Pachucki, Krzysztof; Komasa, Jacek
A novel perturbation theory has been developed to account for nonadiabatic effects in diatomic molecules, 164113 (2009)}. All molecular levels can be obtained simultanously from a single nuclear equation corrected for the presence of $(m/M)^2$ terms. Comparison with the direct nonadiabatic calculations for rotationless states of H$_2$ demonstrates an agreement at the level of $10^{-5}$ cm$^{-1}$ for the ground tone transition.
Author Institution: Faculty of Physics, University of Warsaw; Ho\.za 69, 00-681 Warsaw, Poland; Faculty of Chemistry, A. Mickiewicz University; Grunwaldzka 6, 60-780 Poznan, Poland
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555892013-01-01T00:00:00ZPachucki, KrzysztofKomasa, JacekTOWARDS MORE ACCURATE MEASUREMENTS OF THE IONIZATION ENERGY OF MOLECULAR HYDROGENhttp://hdl.handle.net/1811/55588
TOWARDS MORE ACCURATE MEASUREMENTS OF THE IONIZATION ENERGY OF MOLECULAR HYDROGEN
Sprecher, D.; Beyer, M.; Liu, J.; Merkt, F.; Salumbides, E.; Eikema, K. S. E.; Ubachs, W.; Jungen, Ch.
With two electrons and two protons, molecular hydrogen is the simplest molecule displaying all features of a chemical bond. H$_2$ is therefore a fundamental system for testing molecular quantum mechanics and quantum electrodynamics in molecules. The test can be performed by comparing measured and calculated intervals between different rovibronic states of H$_2$ \textbf{107} (4), 043005 (2011).}. Two further quantities that can be used for this test are the dissociation and ionization energies of H$_2$, and considerable efforts have been invested over more than 80 years to improve the precision and accuracy of experimental and theoretical determination of these two quantities. The current status of the comparison is that the theoretical \textbf{5} (11), 3039 (2009).} and experimental \textbf{130} (17), 174306 (2009).} values of the ionization and dissociation energies of H$_2$ agree within the combined uncertainty of 30~MHz (see also \textbf{150}, 51 (2011).}). The factors currently limiting the precision of the experimental determination will be discussed and the strategies that are being implemented towards overcoming these limitations will be presented. A long-term goal is to achieve a precision of better than 15~kHz, which is the ultimate limit imposed on the accuracy of the theoretical determination by the current uncertainty of the proton-to-electron mass ratio.
Author Institution: ETH Zurich, Laboratorium fur Physikalische Chemie, Wolfgang-Pauli-Strasse 10, 8093 Zurich, Switzerland; Department of Physics and Astronomy, Laser Centre, Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands; Laboratoire Aime Cotton, CNRS II, Batiment 505, Campus d'Orsay, 91405 Orsay Cedex, France
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555882013-01-01T00:00:00ZSprecher, D.Beyer, M.Liu, J.Merkt, F.Salumbides, E.Eikema, K. S. E.Ubachs, W.Jungen, Ch.PRECISE MEASUREMENT OF VIBRATIONAL TRANSITION FREQUENCY OF OPTICALLY TRAPPED MOLECULEShttp://hdl.handle.net/1811/55587
PRECISE MEASUREMENT OF VIBRATIONAL TRANSITION FREQUENCY OF OPTICALLY TRAPPED MOLECULES
Kajita, Masatoshi; Gopakumar, Geetha; Abe, Minori; Hada, Masahiko
We propose to measure the $X^{2}\Sigma\left( v,N,F,M\right) =\left( 0,0,3/2,\pm3/2\right) \rightarrow\left( v_{u},0,3/2,\pm3/2\right) \left( v_{u}=1,2,3,4,,,,\right) $ transition frequencies of X$^{6}$Li molecules with the uncertainty lower than 10$^{-16}$ (X: $^{174}$Yb, $^{88}$Sr, $^{40}$Ca). Molecules are produced by photo-association of cold atoms and trapped in the optical lattices. Measurement with molecules in optical lattices is particularly advantageous for precision measurements because (1) the molecules and probe laser interact for a long time, (2) molecules are localized within the Lamb-Dicke region, (3) the measurement is possible with a large number of molecules, and (4) collision effects are suppressed (molecules are trapped at different positions in 2D lattices). Using the proper trap laser frequency, the Stark shift induced by the trap laser is eliminated as the Stark energy shift of the upper and lower states are equal (magic frequency). When the trap laser frequency is shifted from the magic frequency by 1 MHz, the Stark shift is less than $3\times10^{-15}$. The $N=0\rightarrow0$ transition is one-photon forbidden, and it is stimulated by Raman transition using two lasers. When one of two Raman lasers is higher than the magic frequency and another is lower, the total Stark shift induced by two Raman lasers can be eliminated. Measurement of molecular vibrational transition frequencies is useful to test the variation in the proton-to-electron mass ratio. The $^{1}$S$_{0}$-$^{3}% $P$_{0}$ transition frequencies of $^{27}$Al$^{+}$ ion or $^{87}$Sr atom are useful as the reference.
Author Institution: Nat. Ins. Info. Comm. Tech., Koganei, Tokyo 184-8795, Japan; Dep. of Chemistry, Tokyo Metro. Univ., Hachioji, Tokyo 192-0397, Japan
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555872013-01-01T00:00:00ZKajita, MasatoshiGopakumar, GeethaAbe, MinoriHada, MasahikoPRECISE MEASUREMENT OF $^{40}$CaH$^{+}$ VIBRATIONAL TRANSITION FREQUENCYhttp://hdl.handle.net/1811/55586
PRECISE MEASUREMENT OF $^{40}$CaH$^{+}$ VIBRATIONAL TRANSITION FREQUENCY
Kajita, Masatoshi; Abe, Minori
Small number of molecular ions in a linear trap can be sympathetically cooled with atomic ions and form a string crystal at the position, where the electric field is zero. Molecular ions in a strinc crystal are advantageous to measure the transition frequencies without Stark shift induced by the trap electric field, but it is required to localize small number of molecular ions in a single quantum state. $^{40}$CaH$^{+}$ molecular ion is advantageous to solve this problem, because (1) molecular ion with rotational constant of 141 GHz is localized in the vibrational-rotational ground state when the surrounding temperature is lower than 10 K, and\ (2) there is no hyperfine splitting in the $J=0$ state. In this presentation, we porpose to measure the $^{40}$CaH$^{+}$ $X^{1}% \Sigma\left( v,N,F,M\right) =\left( 0,0,1/2,\pm1/2\right) \rightarrow \left( v_{u},0,1/2,\pm1/2\right) \left( v_{u}=1,2,3,,,\right) $ transition with the uncertainty lower than 10$^{-16}$. With these transitions, Zeeman shift is less than 10$^{-16}$/G (given by the slight dependence of schielding effect by electron cloud on the vibrational state) and electric quadrupole shift is zero because of $F=1/2$. The $J=0\rightarrow0$ transition is one-photon forbidden, and it can be observed also by Raman transition using two lasers. Stark shift induced by Raman lasers actually dominates the measurement uncertainty. When $v=0\rightarrow1$ transition is observed using Raman lasers in the 6000-15000 /cm, Stark shift with saturation power is of the order of $1.5\times10^{-14}$ and it is higher for overtone transitions. With the following Raman laser frequencies, total Stark shift induced by two Raman lasers is zero. $\ \ \ v=0\rightarrow1$ \ 24527 /cm and 23079 /cm $\ \ \ \ v=0\rightarrow2$ \ 24600 /cm and 21745 /cm \ \ $\ \ v=0\rightarrow3$ \ 26237 /cm and 22017 /cm \ $\ \ v=0\rightarrow4$ \ 25354 /cm and 19814 /cm The $^{40}$CaH$^{+}$ $X^{1}\Sigma\left( v,N,F,M\right) =\left( 0,0,1/2,\pm1/2\right) \rightarrow\left( v_{u},0,1/2,\pm1/2\right) \left( v_{u}=1,2,3,,,\right) $ transition can be measured with the uncertainty lower than 10$^{-16}$, and it is useful to test the variation in the proton-to-electron mass ratio.
Author Institution: Nat. Ins. Info. Comm. Tech., Koganei, Tokyo 184-8795, Japan; Dep. of Chemistry, Tokyo Metro. Univ., Hachioji, Tokyo 192-0397, Japan
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555862013-01-01T00:00:00ZKajita, MasatoshiAbe, MinoriTHE CO A-X SYSTEM FOR CONSTRAINING COSMOLOGICAL DRIFT OF THE PROTON-ELECTRON MASS RATIOhttp://hdl.handle.net/1811/55585
THE CO A-X SYSTEM FOR CONSTRAINING COSMOLOGICAL DRIFT OF THE PROTON-ELECTRON MASS RATIO
Niu, M. L.; Salumbides, E. J.; Zhao, D.; Bagdonaite, J.; De Oliveira, N.; Joyeux, D.; Nahon, L.; Field, R. W.; Ubachs, W.
The $\textrm{A}^1\Pi-\textrm{X}^1\Sigma^+$ band system of carbon monoxide, which has been detected in six highly redshifted galaxies ($z=1.6-2.7$), is identified as a novel probe method to search for possible variations of the proton-electron mass ratio ($\mu$) on cosmological time scales. Laboratory wavelengths of the spectral lines of the A-X ($v$,0) bands for $v=0-9$ have been determined at an accuracy of $\Delta\lambda/\lambda=1.5 \times 10^{-7}$ through VUV Fourier-transform absorption spectroscopy, providing a comprehensive and accurate zero-redshift data set. Two-photon Doppler-free laser spectroscopy has been applied for the (0,0) and (1,0) bands, achieving $3 \times 10^{-8}$ accuracy level, verifying the absorption data. Accurate sensitivity coefficients $K_{\mu}$ for a varying $\mu$ have been calculated for the CO A-X bands, so that an operational method results to search for $\mu$-variation. The data from both experiments were used to perform an improved analysis of the perturbations in the A$^1\Pi$, $v=0$ and 1 levels by vibrational levels in the D$^1\Delta$, I$^1\Sigma^-$, e$^3\Sigma^-$, d$^3\Delta$, and a$'^3\Sigma^+$ states. The object Q1237+064 will be observed in May 2013, aiming for a good signal-to-noise spectrum containing the CO A-X bands as well as the H$_2$ Lyman and Werner bands. This should result in an accurate and robust constraint on $\Delta\mu/\mu$.
Author Institution: Department of Physics and Astronomy, and LaserLaB, VU University, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands; Synchrotron Soleil, Orme des Merisiers, St Aubin BP 48, 91192, GIF sur Yvette cedex, France; Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA; Department of Physics and Astronomy, and LaserLaB, VU University, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555852013-01-01T00:00:00ZNiu, M. L.Salumbides, E. J.Zhao, D.Bagdonaite, J.De Oliveira, N.Joyeux, D.Nahon, L.Field, R. W.Ubachs, W.SUB-DOPPLER AND FTMW SPECTROSCOPY OF HC$_3$N ISOTOPOLOGUEShttp://hdl.handle.net/1811/55584
SUB-DOPPLER AND FTMW SPECTROSCOPY OF HC$_3$N ISOTOPOLOGUES
Lapinov, A. V.; Golubiatnikov, G. Yu.; Velmuzhov, A. P.; Grabow, J.-U.; Guarnieri, A.
We report results of precise sub-Doppler spectroscopy of HC$_3$N, H$^{13}$CCCN,\ HC$^{13}$CCN, HCC$^{13}$CN and HCCC$^{15}$N at 45$-$510~GHz with Lamb-dip spectrometer of IAP RAS. Hf structure of rotational transitions of all above species below 27 GHz as well as inversion transitions of NH$_3$(1,1) and (2,2) were measured using FTMW spectrometer of University of Hannover. New comparison of HC$_3$N and NH$_3$ laboratory frequencies with radio astronomical observations of dark clouds% nderline{\textbf{524}}, A32, 2010.}$^,$% nderline{\textbf{512}}, A44, 2010.} shows an upper limit of $m_e/m_p$ variation in our Galaxy as $\le3\cdot10^{-9}$.
Author Institution: Institute of Applied Physics of RAS, 46 Ulyanov str., 603950 Nizhny Novgorod, Russia; Institute of Metalloorganic Chemistry of RAS, 49 Tropinin str., 603950 Nizhny Novgorod, Russia; Institute of Physical Chemistry and Electrochemistry, Leibniz University of Hannover, Callinstrasse 3A, 30167 Hannover, Germany; Technical Faculty of Christian Albrecht University of Kiel, Kaiserstrasse 2, 24143 Kiel, Germany
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555842013-01-01T00:00:00ZLapinov, A. V.Golubiatnikov, G. Yu.Velmuzhov, A. P.Grabow, J.-U.Guarnieri, A.THE CM-, MM- AND SUBMM-WAVE SPECTRUM OF ALLYL ISOCYANIDE AND RADIOASTRONOMICAL OBSERVATIONS IN ORION KL AND THE PRIMOS LINE SURVEYhttp://hdl.handle.net/1811/55583
THE CM-, MM- AND SUBMM-WAVE SPECTRUM OF ALLYL ISOCYANIDE AND RADIOASTRONOMICAL OBSERVATIONS IN ORION KL AND THE PRIMOS LINE SURVEY
Haykal, I.; Motiyenko, R. A.; Margules, L.; Huet, T. R.; Ecija, P.; Cocinero, E. J.; Basterretxea, F.; Fernandez, J. A.; Castano, F.; Tercero, B.; Cernicharo, J.; Lesarri, A.; Guillemin, J. C.
Last year we presented the first rotational analysis of the ground state of the two conformers of allyl isocyanide from 4 GHz to 905 GHz. The analysis of the rotational spectrum of the cis conformer of allyl isocyanide was extended. We resolved Coriolis interactions of $a$ and $b$ types between the excited vibrational states $\nu_1=1$ and $\nu_2=1$, calculated to be at 156 $cm^{-1}$ ($A^{'}$) and 167 $cm^{-1}$ ($A^{''}$) respectively (MP2/aug-cc-pvtz), from 150 GHz to 600 GHz}. Strong perturbations were observed in the 150-310 GHz range for low values of the quantum number $K_a$ starting from $K_a = 0, 1$. The anharmonicities appeared as well at higher frequencies for larger quantum numbers. The two modes were fitted together with the SPFIT/SPCATnderline{\textbf{148}}, 371-377, 1991.} suite of programs and a set of Coriolis parameters was accurately determined. The fit contains more than 3000 lines up to $J = 99$ and $K_a = 12$ for both modes. We did not detect these species neither in the IRAM 30-m line survey of Orion KL nor in the PRIMOS survey towards SgrB2. Nevertheless, we provided upper limits to their column density in Orion KL. \em{This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI.} %The fit contains more than 3000 lines up to $J = 99$ and $k_a = 12$ for both modes. The proceeding of the analysis to higher $k_a$ quantum numbers showed even more complications due to additional interactions with $\nu_3=1$ and $\nu_4=1$. %Zero-kinetic-energy (ZEKE) photoelectron spectroscopy was used to probe the vibrational levels in the ground electronic state of the chlorobenzene cation using a two-color photoionization scheme via the S${_1}$ electronic state of the neutral nderline{\textbf{102}}(12), XXXX March 1995.}. Exciting through different S${_1}$ vibrational levels has revealed mixing of some S${_1}$ normal coordinates in the ground state of the cation. A previously-identified Fermi resonance in the S${_1}$ state of the neutral is also confirmed by the ZEKE spectra. The adiabatic ionization energy is measured as $73\,170\pm5$\,cm$^{-1}$.
Author Institution: Laboratoire PhLAM, UMR8523 CNRS-Universite Lille 1, F-59655 Villeneuve d'Ascq Cedex, France; Departamento de Quimica Fisica, Facultad de Ciencia y Tenologia, Universidad del Pais Vasco, Barrio Sarriena s/n, 48940 Leioa (Spain); Centro de Astrobiologia (CSIC-INTA). Ctra de Ajalvir, Km 4, 28850 Torrejon de Ardoz, Madrid, Spain; Departamento de Quimica Fisica y Quimica Inorganica, Facultad de Ciencias, Universidad de Valladolid, 47011 Valladolid (Spain); Sciences Chimiques de Rennes -Ecole Nationale Superieure de Chimie de Rennes -CNRS -35700 Rennes, France
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555832013-01-01T00:00:00ZHaykal, I.Motiyenko, R. A.Margules, L.Huet, T. R.Ecija, P.Cocinero, E. J.Basterretxea, F.Fernandez, J. A.Castano, F.Tercero, B.Cernicharo, J.Lesarri, A.Guillemin, J. C.HIGH RESOLUTION MICROWAVE SPECTROSCOPY OF CH AS A SEARCH FOR VARIATION OF FUNDAMENTAL CONSTANTShttp://hdl.handle.net/1811/55582
HIGH RESOLUTION MICROWAVE SPECTROSCOPY OF CH AS A SEARCH FOR VARIATION OF FUNDAMENTAL CONSTANTS
Truppe, S.; Hendricks, R. J.; Tokunaga, S. K.; Hinds, E. A.; Tarbutt, M. R.
The Standard Model of particle physics assumes that fundamental, dimensionless constants like the fine-structure constant, $\alpha$, or the ratio of the proton to electron mass, $\mu$, remain constant through time and space. Laboratory experiments have set tight bounds on variations of such constants on a short time scale nderline{\textbf{319}}(5871), 1808, 2008}. Astronomical observations, however, provide vital information about possible changes on long time scales. Recent measurements using quasar absorption spectra provide some evidence for a space-time variation of the fine-structure constant $\alpha$ nderline{\textbf{107}}(19), 191101, 2011}. It is thus important to verify this discovery by using an entirely different method. Recently the prospect of using rotational microwave spectra of molecules as a probe of fundamental constants variation has attracted much attention nderline{\textbf{99}}(15), 150801, 2007}. Generally these spectra depend on $\mu$, but if fine and hyperfine structure is involved they also become sensitive to variations of $\alpha$ and the nuclear g-factor. Recent calculations nderline{\textbf{80}}(2), 022118, 2009}$^{,}$ nderline{\textbf{86}}(3), 032501, 2012} show that the $\Lambda$-doublet and rotational spectra of CH are particularly sensitive to possible variations of $\mu$ and $\alpha$. We present recent laboratory based high-resolution spectra of the $\Lambda$-doublet transition frequencies of the $\mathcal{F}_2$, $J=1/2$ and $\mathcal{F}_1$, $J=3/2$ states of CH, $X^{2}{\Pi}$~(v=0) at 3.3GHz and 0.7GHz respectively, with $\mathcal{F}$ labelling the different spin-orbit manifolds of CH. We also present a measurement of the transition frequency between the two spin-orbit manifolds $\mathcal{F}_2$, J=1/2 and $\mathcal{F}_1$, J=3/2 at 530GHz. By using a molecular beam of CH in combination with a laser-microwave double-resonance technique and Ramsey's method of separated oscillatory fields, we have measured these transition frequencies to unprecedented accuracy. Hence CH can now be used as a sensitive probe to detect changes in fundamental constants by comparing lab based frequencies to radio-astronomical observations from distant gas clouds.
Author Institution: Centre for Cold Matter, Blackett Laboratory, Imperial College London, London, SW7 2BW
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555822013-01-01T00:00:00ZTruppe, S.Hendricks, R. J.Tokunaga, S. K.Hinds, E. A.Tarbutt, M. R.CH$_3$OH SUB-DOPPLER SPECTROSCOPYhttp://hdl.handle.net/1811/55581
CH$_3$OH SUB-DOPPLER SPECTROSCOPY
Golubiatnikov, German Yu.; Belov, Sergey P.; Lapinov, Alexander V.
The methanol torsion-rotation spectrum in the first three torsional states has been measured and analysed for a search of $m_e/m_p$ variations from comparison of radio astronomical and laboratory frequencies and for studies of systematic velocity motions in star-forming regions. The investigation is based on Lamb-dip measurements with sub-Doppler spectrometer developed at IAP RAS. CH$_3$OH-A and -E frequencies have been obtained with an accuracy of $\sim$1 kHz at 48$-$510~GHz for more than 500 transitions in $v_t=0$, more than 200 transitions in $v_t=1$ and 100 transitions in $v_t=2$. For many b-type transitions the removed degeneracy of the CH$_3$OH levels due to different nuclear spin statistics was measured in a form of doublets with unresolved hf structure. Some a-type transitions show resolved spin-rotational splitting.
Author Institution: Institute of Applied Physics of RAS, 46 Ulyanov str., 603950 Nizhny Novgorod, Russia
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555812013-01-01T00:00:00ZGolubiatnikov, German Yu.Belov, Sergey P.Lapinov, Alexander V.SENSITIVITY OF TRANSITIONS IN INTERNAL ROTOR MOLECULES TO A POSSIBLE VARIATION OF THE PROTON-TO-ELECTRON MASS RATIOhttp://hdl.handle.net/1811/55580
SENSITIVITY OF TRANSITIONS IN INTERNAL ROTOR MOLECULES TO A POSSIBLE VARIATION OF THE PROTON-TO-ELECTRON MASS RATIO
Jansen, P.; Ubachs, W.; Bethlem, H. L.; Kleiner, I.; Xu, L-H.
Recently, methanol was identified as a sensitive target system to probe variations of the proton-to-electron mass ratio. The high sensitivity of methanol originates from the interplay between overall rotation and hindered internal rotation of the molecule and it gives rise to a large enhancement of the sensitivity coefficient,$K_{\mu}$. In this talk we will remind the general concepts that form the foundation of the high sensitivity in methanol and the approximate model which allows to estimate the sensitivities of transitions in internal rotor molecules with $C_{3v}$ symmetry, without performing a full calculation of energy levels. We will show some examples by comparing obtained sensitivities for methanol, acetaldehyde, acetamide, methyl formate and acetic acid with a full analysis using the molecular Hamiltonian. The talk will give some details about how we obtain the energy levels from the BELGI code. From the molecules considered, methanol appears to be the most suitable candidate for laboratory and cosmological tests searching for a possible variation of \mu.
Author Institution: Institute for Lasers, Life and Biophotonics, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands; Laboratoire Interuniversitaire des Systemes Atmospheriques, CNRS et Universites Paris Diderot et; Paris Est, 61 av. General de Gaulle, 94010; Creteil, France; Department of Physics and Centre for Laser, Atomic and Molecular Sciences, University of New Brunswick, Saint John, New Brunswick E2L 4L5, Canada
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555802013-01-01T00:00:00ZJansen, P.Ubachs, W.Bethlem, H. L.Kleiner, I.Xu, L-H.SEARCH FOR A VARIATION OF FUNDAMENTAL CONSTANTShttp://hdl.handle.net/1811/55578
SEARCH FOR A VARIATION OF FUNDAMENTAL CONSTANTS
Ubachs, W.
Since the days of Dirac scientists have speculated about the possibility that the laws of nature, and the fundamental constants appearing in those laws, are not rock-solid and eternal but may be subject to change in time or space. Such a scenario of evolving constants might provide an answer to the deepest puzzle of contemporary science, namely why the conditions in our local Universe allow for extreme complexity: the fine-tuning problem. In the past decade it has been established that spectral lines of atoms and molecules, which can currently be measured at ever-higher accuracies, form an ideal test ground for probing drifting constants. This has brought this subject from the realm of metaphysics to that of experimental science. In particular the spectra of molecules are sensitive for probing a variation of the proton-electron mass ratio $\mu$, either on a cosmological time scale, or on a laboratory time scale. A comparison can be made between spectra of molecular hydrogen observed in the laboratory and at a high redshift (z=2-3), using the Very Large Telescope (Paranal, Chile)~ and the Keck telescope (Hawaii)~. This puts a constraint on a varying mass ratio $\Delta\mu/\mu$ at the $10^{-5}$ level. The optical work can also be extended to include CO molecules~. Further a novel direction will be discussed: it was discovered that molecules exhibiting hindered internal rotation have spectral lines in the radio-spectrum that are extremely sensitive to a varying proton-electron mass ratio. Such lines in the spectrum of methanol were recently observed with the radio-telescope in Effelsberg (Germany).
Author Institution: Department of Physics and Astronomy, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, Netherlands
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555782013-01-01T00:00:00ZUbachs, W.AN ALCOHOL TEST FOR DRIFTING CONSTANTShttp://hdl.handle.net/1811/55579
AN ALCOHOL TEST FOR DRIFTING CONSTANTS
Jansen, P.; Bagdonaite, J.; Ubachs, W.; Bethlem, H. L.; Kleiner, I.; Xu, L.-H.
The Standard Model of physics is built on the fundamental constants of nature, however without providing an explanation for their values, nor requiring their constancy over space and time. Molecular spectroscopy can address this issue. Recently nderline{\textbf{106}}(100801) 2011.}, we found that microwave transitions in methanol are extremely sensitive to a variation of the proton-to-electron mass ratio $\mu$, due to a fortuitous interplay between classically forbidden internal rotation and rotation of the molecule as a whole. In this talk, we will explain the origin of this effect and how the sensitivity coefficients in methanol are calculated. In addition, we set a limit on a possible cosmological variation of $\mu$ by comparing transitions in methanol observed in the early Universe with those measured in the laboratory. Based on radio-astronomical observations of PKS1830-211, we deduce a constraint of $\Delta\mu/\mu=(0.0\pm 1.0)\times 10^{-7}$ at redshift $z = 0.89$, corresponding to a look-back time of 7 billion years nderline{\textbf{339}}(46) 2013.}. While this limit is more constraining and systematically more robust than previous ones, the methanol method opens a new search territory for probing $\mu$-variation on cosmological timescales.
Author Institution: Institute for Lasers, Life and Biophotonics, VU University Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands; Laboratoire Interuniversitaire des Systemes Atmospheriques (LISA), CNRS UMR 7583 et Universites Paris Diderot et Paris Est, 61 av. General de Gaulle, 94010 Creteil Cedex, France; Department of Physics and Centre for Laser, Atomic, and Molecular Sciences, University of New Brunswick, Saint John, New Brunswick E2L 4L5, Canada
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555792013-01-01T00:00:00ZJansen, P.Bagdonaite, J.Ubachs, W.Bethlem, H. L.Kleiner, I.Xu, L.-H.LINEAR AND NONLINEAR MOLECULAR SPECTROSCOPY WITH LASER FREQUENCY COMBShttp://hdl.handle.net/1811/55577
LINEAR AND NONLINEAR MOLECULAR SPECTROSCOPY WITH LASER FREQUENCY COMBS
Picque, Nathalie
The regular pulse train of a mode-locked femtosecond laser can give rise to a comb spectrum of millions of laser modes with a spacing precisely equal to the pulse repetition frequency. Laser frequency combs were conceived a decade ago as tools for the precision spectroscopy of atomic hydrogen. They are now becoming enabling tools for an increasing number of applications, including molecular spectroscopy. Recent experiments of multi-heterodyne frequency comb Fourier transform spectroscopy (also called dual-comb spectroscopy) have demonstrated that the precisely spaced spectral lines of a laser frequency comb can be harnessed for new techniques of linear absorption spectroscopy. The first proof-of-principle experiments have demonstrated a very exciting potential of dual-comb spectroscopy without moving parts for ultra-rapid and ultra-sensitive recording of complex broad spectral bandwidth molecular spectra. Compared to conventional Michelson-based Fourier transform spectroscopy, recording times could be shortened from seconds to microseconds, with intriguing prospects for spectroscopy of short lived transient species. The resolution improves proportionally to the measurement time. Therefore longer recordings allow high resolution spectroscopy of molecules with extreme precision, since the absolute frequency of each laser comb line can be known with the accuracy of an atomic clock. Moreover, since laser frequency combs involve intense ultrashort laser pulses, nonlinear interactions can be harnessed. Broad spectral bandwidth ultra-rapid nonlinear molecular spectroscopy and imaging with two laser frequency combs is demonstrated with coherent Raman effects and two-photon excitation. Real-time multiplex accessing of hyperspectral images may dramatically expand the range of applications of nonlinear microscopy.
Author Institution: Max Planck Institut fur Quantenoptik, Hans-Kopfermann-Str. 1, 85748 Garching, Germany; Ludwig-Maximilians-Universitat Munchen, Fakultat fur Physik, Schellingstrasse 4/III, 80799 Munchen, Germany; Institut des Sciences Moleculaires d'Orsay, Universite Paris-Sud, 91405 Orsay, France; email: nathalie.picque@mpq.mpg.de;
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555772013-01-01T00:00:00ZPicque, NathalieDECODING THE EFFECTS OF LARGE AMPLITUDE VIBRATIONAL MOTIONS IN SPECTRAhttp://hdl.handle.net/1811/55576
DECODING THE EFFECTS OF LARGE AMPLITUDE VIBRATIONAL MOTIONS IN SPECTRA
McCoy, Anne B.; Dzugan, Laura C.; Huang, Meng; Lin, Zhou; Opoku-Agyeman, Bernice; Petit, Andrew S.; Ford, Jason; Wellen, Bethany A.
Over the past decades significant progress has been made, which allows spectroscopists to interpret vibrational spectra of molecules that undergo small amplitude displacements from their equilibrium structure. Based on these assignments, one can obtain insights into the structure and bonding of the molecule that is being studied through the use of model Hamiltonians. In this talk, we focus on systems that undergo large amplitude vibrational motions, and where the anharmonicities are manifested in unexpected intensity patterns in the vibrational spectrum. Theoretical and computational approaches used to address such questions will be described, with an emphasis on our group's work on diffusion Monte Carlo approaches. The ideas will be illustrated through discussions of a variety of protonated and hydrogen bonded systems of current experimental interest including H$_5^+$, molecules and ions that have intermolecular hydrogen bonds, and ion-water complexes.
Author Institution: Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555762013-01-01T00:00:00ZMcCoy, Anne B.Dzugan, Laura C.Huang, MengLin, ZhouOpoku-Agyeman, BernicePetit, Andrew S.Ford, JasonWellen, Bethany A.LOW TEMPERATURE TRAPPING: FROM REACTIONS TO SPECTROSCOPYhttp://hdl.handle.net/1811/55575
LOW TEMPERATURE TRAPPING: FROM REACTIONS TO SPECTROSCOPY
Schlemmer, S.; Asvany, O.; Brunken, S.
The kinetics of ion - molecule reactions are investigated in higher-order multipole traps by observation of the temporal evolution of mass selected parent ions in the presence of a neutral reaction partner. Rate coeffients for fast reactions (proceeding at collision rate) and very slow reactions (taking millions of collisions) are determined over a wide range of temperatures. Endothermic or hindered reactions can be promoted by excitation of the ion via absorption of a photon. Scanning the photon energy while detecting the number of product ions establishes an action spectroscopy method which we developed over the last 10-15 years and termed LIR: laser or light induced reactions. % % The main advantages of LIR are mass selection of the parent ion and low temperature conditions in the trap. Long storage times in combination with a near unity detection efficiency make LIR one of the most sensitive spectroscopy methods. The status quo of LIR will be discussed on selected examples. Recent measurements are concerned with ro-vibrational spectra of CH$_2$D$^+$ % % and CH$_5^+$ % % at highest resolution using cw OPO radiation. In the particular case of CH$_5^+$, the lines in the mid IR have been measured at a nominal temperature of 10 K and a frequency comb has been used for absolute calibration. Line positions can be determined to an accuracy which shall enable us in the future to obtain rotational spectra in a THz-IR double resonance approach. We tested the feasibility of this two photon method recently on H$_2$D$^+$. %
Author Institution: I. Physikalisches Institut, Universitat zu Koln, 50937 Koln, Germany
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555752013-01-01T00:00:00ZSchlemmer, S.Asvany, O.Brunken, S.USING TERAHERTZ SPECTROSCOPY TO STUDY SYSTEMS WITH SOLAR ENERGY APPLICATIONShttp://hdl.handle.net/1811/55574
USING TERAHERTZ SPECTROSCOPY TO STUDY SYSTEMS WITH SOLAR ENERGY APPLICATIONS
Milot, Rebecca L.; Moore, Gary F.; Martini, Lauren A.; Brudvig, Gary W.; Crabtree, Robert H.; Schmuttenmaer, Charles A.
Biomimetic solar water oxidation systems are being developed as renewable alternatives to fossil fuels. One possible design incorporates thin-film dye-sensitized nanoparticle photoanades to capture and convert visible light to charge carriers and catalysts to facilitate water oxidation. The physical properties of the dye are important due to its position as the light absorber and electron transfer initiator. Given the role that porphyrins play in photosynthesis and their synthetic tunability, they are promising components for these photoanodes. Time-Resolved THz Spectroscopy (TRTS), an optical pump/THz probe technique, is a non-contact electrical probe with proven usefulness for studying electron transfer and conductivity on a sub-picosecond timescale. Using TRTS, the efficiency and dynamics of electron injection from porphyrin dyes into metal oxide surfaces was found to be strongly influenced by the structure and photophysical properties of the dye.
Author Institution: Department of Chemistry, Yale University, New Haven, CT 06520-8107
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555742013-01-01T00:00:00ZMilot, Rebecca L.Moore, Gary F.Martini, Lauren A.Brudvig, Gary W.Crabtree, Robert H.Schmuttenmaer, Charles A.DETECTION AND INTERPRETATION OF COLLISIONAL TRANSFER AND ROTATIONAL ANISOTROPY FINGERPRINTS IN RESONANT FOUR-WAVE MIXING SPECTRAhttp://hdl.handle.net/1811/55573
DETECTION AND INTERPRETATION OF COLLISIONAL TRANSFER AND ROTATIONAL ANISOTROPY FINGERPRINTS IN RESONANT FOUR-WAVE MIXING SPECTRA
Kouzov, A.; Radi, P.; Maksyutenko, P.; Kozlov, D.
Coherent responses produced by resonant four-wave mixing (RFWM) in a weakly absorbing medium carry valuable information on the intrinsic properties and dynamics of the quantum states involved. Here, two aspects of RFWM applications are highlighted. \ First, the Two-Color (TC) version of RFWM was found to be a unique spectroscopic tool to directly trace collisional state-to-state transfer in isotropic gaseous media, both in the frequency% , 271 (1997).} and time, 3911 \ (2007).} domains. Second, the RFWM techniques appeared to be very useful for studies of the rotational anisotropy, 6314 (1997).}. Here we report new experimental one-color RFWM spectra of the OH radicals produced by laser photolysis of H$_{2}$O$_{2}$ at 266 nm. Polarization dependence and Doppler line structure of the spectra show clear evidence of the pronounced anisotropy of angular momentum (\textbf{j}) and velocity (% \textbf{v}) distributions as well as on the \textbf{j-v} correlation. The obtained results directly point to the pronounced OH helicity (i.e. \textbf{j% }$\parallel $\textbf{v}) which yet remained beyound the reach of purely optical means. For all mentioned cases, the line-shape theory, 010701 (2000).} is an optimal tool to derive compact expressions for the RFWM signals. The work was supported by the Swiss Federal Office of Energy, the Swiss National Science Foundation (200020\_124542/1), and by the Russian Foundation for Basic Research, grants 11-02-01296 and 11-03-00448.
Author Institution: Department of Physics, Saint-Petersburg State University, Peterhof, Saint-Petersburg 198504, Russia; Department General Energy, Paul Scherrer Institute, CH-5232 Villigen, Switzerland; A.M. Prokhorov General Physics Institute, Russian Academy of Sciences; Vavilov str. 38, 119991 Moscow, Russia
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555732013-01-01T00:00:00ZKouzov, A.Radi, P.Maksyutenko, P.Kozlov, D.STRUCTURE OF THE DENSE MOLECULAR GAS IN THE HELIX NEBULA: LARGE SCALE MAPPING OF HCO$^{+}$http://hdl.handle.net/1811/55572
STRUCTURE OF THE DENSE MOLECULAR GAS IN THE HELIX NEBULA: LARGE SCALE MAPPING OF HCO$^{+}$
Zeigler, N. R.; Ziurys, L. M.; Zack, L. N.
The Helix Nebula, NGC 7293, has been mapped in HCO$^{+}$ J = 1 $\rightarrow$ 0 emission with a 70$^{\prime}$$^{\prime}$ spatial resolution (1.68 km s$^{-1}$ velocity resolution) using the Arizona Radio Observatory (ARO) 12 m telescope on Kitt Peak. Over 200 individual positions covering an area of roughly 1000 $\times$ 800 $^{\prime}$$^{\prime}$ were observed down to a 3$\sigma$ noise level of \textasciitilde 20 mK. HCO$^{+}$ was detected at over three-quarters of the positions, with the majority of spectra showing multiple velocity components indicative of a complex kinematic structure. The column density of HCO$^{+}$ across the Helix ranges from N$_{tot}$ $\~{}$ 1.4 $\times$ 10$^{11}$ to $\~{}$2.4 $\times$ 10$^{12}$ cm$^{-2}$, with an average N$_{tot}$ $\~{}$ 4 $\times$ 10$^{11}$ cm$^{-2}$. The HCO$^{+}$ distribution, which traces gas with densities \textasciitilde 10$^{5}$ cm$^{-3}$, is similar to that of CO and H$_{2}$ , with certain point symmetries and red-and blue-shifted regions common in all three molecules; these data are also consistent with observations of atomic lines. The HCO$^{+}$ emission appears to trace two ring-like structures emanating from the central star: one is blue-shifted and the other red-shifted with respect to the star, and possibly trace the edges of a bipolar outflow.
Author Institution: Department of Chemistry, University of Arizona, PO Box 210041, 1306 East University Blvd, Tucson, AZ, 85721, USA; Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555722013-01-01T00:00:00ZZeigler, N. R.Ziurys, L. M.Zack, L. N.STUDY OF PROTON TRANSFER IN \textit{E. COLI} PHOTOLYASEhttp://hdl.handle.net/1811/55571
STUDY OF PROTON TRANSFER IN \textit{E. COLI} PHOTOLYASE
Zhang, Meng; Liu, Zheyun; Li, Jiang; Wang, Lijuan; Zhong, Dongping
Photolyase is a flavoprotein which utilizes blue-light energy to repair UV-light damaged DNA. The catalytic cofactor of photolyase, flavin adenine dinucleotide (FAD), has five redox states. Conversions between these redox states involve intraprotein electron transfer and proton transfer, which play important role in protein function. Here we systematically studied proton transfer in \textit{E. coli} photolyase \textit{in vitro} by site-directed mutagenesis and steady-state UV-vis spectroscopy, and proposed the proton channel in photolyase. We found that in the mutant N378C/E363L, proton channel was completely eliminated when DNA substrate was bound to the protein. Proton is suggested to be transported from protein surface to FAD by two pathways: the proton relay pathway through E363 and surface water to N378 and then to FAD; and the proton diffusion pathway through the substrate binding pocket. In addition, reaction kinetics of conversions between the redox states was then solved and redox potentials of the redox states were determined. These results described a complete picture of FAD redox changes, which are fundamental to the functions of all flavoenzymes.
Author Institution: 191 W. Woodruff Ave., Columbus, Ohio 43210.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555712013-01-01T00:00:00ZZhang, MengLiu, ZheyunLi, JiangWang, LijuanZhong, DongpingPHOTOISOMERIZATION DYANAMICS OF THE SUNSCREEN MOLECULE AVOBENZONEhttp://hdl.handle.net/1811/55570
PHOTOISOMERIZATION DYANAMICS OF THE SUNSCREEN MOLECULE AVOBENZONE
Dunkelberger, Adam D.; Kieda, Ryan D.; Crim, F. Fleming
We report the photoisomerization dynamics of the widely utilized sunscreen molecule avobenzone after near UV excitation at 350 nm. Probing with 266 nm light was utilized to elucidate isomerization dynamics producing what appears to be a twisted form of the initial enol state. Probing with broadband continuum light from 350-600 nm provides a picture of the ground state bleach, excited state dynamics, and subsequent relaxation on the ground state. The combination of these probing techniques provides a comprehensive view of the ultrafast dynamics initiated by absorption at 350 nm.
Author Institution: Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555702013-01-01T00:00:00ZDunkelberger, Adam D.Kieda, Ryan D.Crim, F. FlemingFEMTOSECOND CONICAL INTERSECTION DYNAMICS OF TRYPTOPHAN IN PROTEINS AND VALIDATION OF SLOWDOWN OF HYDRATION LAYER DYNAMICShttp://hdl.handle.net/1811/55569
FEMTOSECOND CONICAL INTERSECTION DYNAMICS OF TRYPTOPHAN IN PROTEINS AND VALIDATION OF SLOWDOWN OF HYDRATION LAYER DYNAMICS
Yang, J.; Zhang, L.; Wang, L.; Zhong, D.
Water motion probed by intrinsic tryptophan shows the significant slowdown around protein surfaces but it is unknown how the ultrafast internal conversion of two nearly degenerate states of Trp ($^1$L$_a$ and $^1$L$_b$) affects the initial hydration in proteins. Here, we used a mini-protein with ten different tryptophan locations one at a time through site-directed mutagenesis and extensively characterized the conversion dynamics of the two states. We observed all the conversion time scales in 40-80 fs by measurement of their anisotropy dynamics. This result is significant and shows no noticeable effect on the initial observed hydration dynamics and unambiguously validates the slowdown of hydration layer dynamics as shown here again in two mutant proteins.
Author Institution: Department of Physics, The Ohio State University, Columbus, OH 43210; Department of Chemistry, Columbia University, New York, NY 10027; Department of Physics, Department of Chemistry and Biochemistry, and Programs of Biophysics, Chemical Physics, and Biochemistry, The Ohio State University, Columbus, OH 43210
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555692013-01-01T00:00:00ZYang, J.Zhang, L.Wang, L.Zhong, D.USING TRYPTOPHAN AS A PROBE FOR STUDYING PROTEIN HYDRATION DYNAMICShttp://hdl.handle.net/1811/55568
USING TRYPTOPHAN AS A PROBE FOR STUDYING PROTEIN HYDRATION DYNAMICS
Qin, Yangzhong; Chang, Chih-Wei; Wang, Lijuan; Zhong, Dongping
Although tryptophan has been used as a probe to study solvation dynamics for decades, a few questions still remain unclear, such as missing of the initial fast component. We proposed a solvation model for construction of the response function of tryptophan probe and carefully investigated the possible initial loss of the ultrafast component with established time-zero emission spectrum and femtosecond-resolved emission spectra (FRES) nderline{\textbf{116}}, 13320, (2012).}. With mutation of GB1 protein, we demonstrated that tryptophan is a powerful probe for protein solvation dynamics and show significant slowdown of the dynamics of hydration shell at protein-water interface.
Author Institution: Department of Physics, The Ohio State University, Columbus, Oh, 43210
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555682013-01-01T00:00:00ZQin, YangzhongChang, Chih-WeiWang, LijuanZhong, DongpingTHEORETICAL STUDIES OF PHOTODISSOCIATION DYNAMICS OF BRCN$^-$http://hdl.handle.net/1811/55567
THEORETICAL STUDIES OF PHOTODISSOCIATION DYNAMICS OF BRCN$^-$
Opoku-Agyeman, Bernice; McCoy, Anne B.
We present the results of theoretical studies of photodissociation dynamics of BrCN$^-$ following electronic excitation to states that dissociate to Br$^-$ + CN and Br$^*$ + CN$^-$. The electronic states were evaluated at the SO-MRCI level of theory with aug-cc-pVTZ basis set using MOLPRO 2010 package. Based on the ~0.05 eV difference between these two asymptotic channels, we anticipate a non-adiabatic interaction similar to that observed in ICN$^-$ will play an important role in the dynamics. In this study, we develop the diabatic models for the two relevant excited states and then study the quantum dynamics of wave packets that are excited to these two states. In the BrCN$^-$ geometry, the two surfaces cross and contain wells that are at least 0.1 eV deep. In contrast, in the BrNC$^-$ geometry, the curves do not cross and only the lower energy diabatic potential contains a well. The overall shape of the excited state potential energy surfaces is expected to play a significant role in the distribution of the photofragments.
Author Institution: Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555672013-01-01T00:00:00ZOpoku-Agyeman, BerniceMcCoy, Anne B.A STUDY OF NbCr AND NbCr$^{-}$ BY ANION PHOTOELECTRON SPECTROSCOPYhttp://hdl.handle.net/1811/55566
A STUDY OF NbCr AND NbCr$^{-}$ BY ANION PHOTOELECTRON SPECTROSCOPY
Baudhuin, Melissa A.; Boopalachandran, Praveenkumar; Rajan, Srijay S.; Leopold, Doreen G.
We report the 488 nm photoelectron spectrum of the NbCr$^{-}$ anion. For the $^{2}\Delta$ ground state of neutral NbCr, the short bond length (1.894 \AA) and high bond energy (D$_0$ 3.0263(6) eV) measured by R2PI spectroscopy indicate high order multiple bonding. We find that the NbCr$^{-}$ anion has a $^{1}\Sigma^{+}$ ground state, in which the "extra" electron occupies the (4d)$\delta$ bonding orbital, giving a $1\sigma^{2}1\pi^{4}1\delta^{4}2\sigma^{2}$ valence electron configuration and a formal bond order of 6. Low-lying excited states of NbCr (assigned as two $^{2}\Sigma^{+}$ states) and NbCr$^{-}$ ($^{3}\Delta$) are also observed. The spectra provide the electron affinity of NbCr, energies of the $^{2}\Sigma^{+}$ and the $^{3}\Delta$ excited states, vibrational frequencies for the NbCr and NbCr$^{-}$ ground states and for the $^{2}\Sigma^{+}$ excited states, and (from Franck-Condon analyses) differences among the bond lengths of the observed states. These results are compared with our previous data for the Group 5/6 congeners NbMo, VCr, and VMo, and with DFT predictions. We also report results for ongoing experiments on the flow tube reactions of the Group V metals Nb and Ta with butadiene, and the vibrationally-resolved photoelectron spectra of some of the organometallic reaction product anions.
Author Institution: Department of Chemistry, University of Minnesota, Minneapolis, MN 55455
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/1811/555662013-01-01T00:00:00ZBaudhuin, Melissa A.Boopalachandran, PraveenkumarRajan, Srijay S.Leopold, Doreen G.